Differsmandatory

Differsmandatory is a coined term used to describe a data validation constraint that combines a difference requirement with a mandatory presence requirement. It applies to a pair of related fields, enforcing that both fields are provided and that their values differ.

The term blends the idea of differ, meaning to be not the same, with mandatory, meaning required. It is not part of any formal standard and does not refer to a widely adopted specification. It appears in informal discussions, tutorials, or design notes as a compact way to describe a composite constraint used in forms, databases, and API schemas.

A typical use case involves two related inputs where both must be supplied but must not be equal. For example, in a password change form, the fields oldPassword and newPassword would be subject to a differsmandatory constraint: oldPassword is filled, newPassword is filled, and oldPassword != newPassword. Similar logic can apply to identifiers, emails, or other paired values where equality would undermine correctness or security.

Implementation considerations include expressing the constraint in the target system. In SQL, it can be represented with a check constraint such as: oldPassword IS NOT NULL AND newPassword IS NOT NULL AND oldPassword <> newPassword. In JSON Schema or form validation frameworks, it typically requires both fields to be required and an additional cross-field inequality check, often via a custom validator.

Related concepts include not-equal constraints, not-null constraints, and composite validations. As a coined term, differsmandatory lacks formal standardization and is mainly encountered in discussion and design contexts.